## Copyright (C) 1995-2011 Friedrich Leisch
##
## This file is part of Octave.
##
## Octave is free software; you can redistribute it and/or modify it
## under the terms of the GNU General Public License as published by
## the Free Software Foundation; either version 3 of the License, or (at
## your option) any later version.
##
## Octave is distributed in the hope that it will be useful, but
## WITHOUT ANY WARRANTY; without even the implied warranty of
## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
## General Public License for more details.
##
## You should have received a copy of the GNU General Public License
## along with Octave; see the file COPYING.  If not, see
## <http://www.gnu.org/licenses/>.

## -*- texinfo -*-
## @deftypefn {Function File} {} triangle_sw (@var{n}, @var{b})
## Triangular spectral window.  Subfunction used for spectral density
## estimation.
## @end deftypefn

## Author: FL <Friedrich.Leisch@ci.tuwien.ac.at>
## Description: Triangular spectral window

function retval = triangle_sw (n, b)

  if (nargin != 2)
    print_usage ();
  endif

  retval = zeros(n,1);
  retval(1) = 1 / b;

  l = (2:n)' - 1;
  l = 2 * pi * l / n;

  retval(2:n) = b * (sin (l / (2*b)) ./ sin (l / 2)).^2;

endfunction